The present invention relates to a clone terminal detection system and method for detecting the presence of a clone mobile station illegally copied from an authentic mobile station.
The presence of clone terminals (clone mobile stations) illegally copied in mobile communication systems such as portable telephones has recently been an important problem. A user having a clone terminal can perform illegal communications free of charge. The fees of the illegal communications are charged to the user having the authentic mobile terminal.
A conventional clone terminal detection method is performed as follows. Key information is stored in both a switching center (or base station) and a mobile terminal. The key information stored in the switching center or base station is compared with that stored in the mobile terminal to detect the presence of a clone terminal. FIGS. 6A and 6B explain a conventional clone terminal detection system described in Japanese Patent Laid-Open No. 10-191457 (reference 1).
As shown in FIG. 6B, a conventional clone terminal detection system comprises a base station 1 having a memory 1a comprised of a nonvolatile memory for storing communication logs and a mobile station 2 having a memory 2a comprised of a nonvolatile memory for storing communication logs.
The operation of the conventional clone terminal detection system having the above arrangement will be described below. Previous communication logs A of communications between the base station 1 and mobile station 2 are stored in the memories 1a and 2a. When the base station 1 communicates with the mobile station 2 (step S1), a communication log B unique to this communication is stored in the memories 1a and 2b of the base and mobile stations 1 and 2. The communication between the base and mobile stations 1 and 2 means a case in which the mobile station 2 communicates with the base station 1 for position registration as soon as the mobile station 1 enters into the communication area of the base station 1, or a case in which the mobile station 2 performs speech communication with the base station 1. An example of the communication log is the date of communication.
A clone mobile station 3 is copied from the mobile station 2 (step S2). At this time, the communication logs A and B stored in the memory 2a of the mobile station 2 are perfectly copied to a memory 3a of the clone mobile station 3. When the clone mobile station 3 communicates with the base station 1 (step S3), a communication log C is stored in the memories 1a and 3a, as shown in FIG. 6B. When the mobile station 2 then communicates with the base station 1 (step S4), a communication log D is stored in the memories 1a and 2a, as shown in FIG. 6B. The memory 1a of the base station 1 stores the communication logs A, B, C, and D, while the memory 2a of the mobile station 2 stores the communication logs A, B, and D.
In the clone terminal detection system, the communication logs stored in the memories 1a and 2a of the base and mobile stations 1 and 2 are compared with each other at a predetermined timing, e.g., every predetermined interval or at the start or end of communication. If the illegal clone mobile terminal 3 is present, the communication logs in the authentic mobile station 2 do not match those of the base station, thereby detecting the presence of the clone mobile station 3.
The conventional technique described above, however, suffers the following problems.
As the first problem, a clone terminal detection function is required in each of the base and mobile stations 1 and 2. That is, the memories 1a and 2a for storing the communication longs are required in the base and mobile stations 1 and 2, respectively.
As the second problem, a special interface is required in a radio zone. That is, the base station 1 must be notified of the communication longs of the mobile station 2 for comparison between the communication logs.
It is an object of the present invention to provide a clone terminal detection system and method capable of detecting the presence of a clone terminal without causing a mobile terminal to have a special function of detecting a clone terminal.
In order to achieve the above object of the present invention, there is provided a clone terminal detection system comprising first storage means for updating and storing position registration information of a mobile terminal, which includes a telephone number, on the basis of a position registration request from one of the mobile terminal and a clone terminal illegally copied from the mobile terminal, comparison means for comparing position registration information of an origination request terminal with the position registration information stored in the first storage means at the time of origination request from one of the mobile and clone terminals, and detection means for detecting the presence of the clone terminal having the same telephone number as that of the mobile terminal on the basis of a comparison result from the comparison means.